1. Field of the Invention
The present invention relates to a wood planing machine, more particularly to a wood planing machine with a height adjustment mechanism that is adapted to be operated externally of a machine body with ease.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional wood planing machine 10 is shown to include a machine base 11, an upper housing 13, and cutting and feed rollers 14.
As illustrated, the machine base 11 has a bed with opposite end portions, a pair of upright threaded rods 23 mounted rotatably on the opposite end portions of the bed, and a pair of vertical side walls 12 mounted on the opposite end portions of the bed. The side walls 12 are formed with front and rear pairs of aligned vertically extending slots 121.
The upper housing 13 is disposed between the side walls 12 above the bed. The upper housing 13 has front and rear portions provided respectively with an opposite pair of insert pieces 21 which engage a corresponding one of the front and rear pairs of vertically extending slots 121 to mount slidably the upper housing 13 on the side walls 12. The upper housing 13 further has opposite end portions formed with a pair of vertically extending screw holes. The threaded rods 23 extend threadedly and respectively through the screw holes, and are rotatable on the bed so as to raise or lower the upper housing 13 to a desired position relative to the bed.
The cutter and feed rollers 14 are mounted rotatably on the upper housing 13, and are rotatable about parallel horizontal axes.
The front and rear sides of the housing 13 are formed with vertical bores for extension of front and rear pairs of upright pillars (not visible) mounted on the machine bed.
The front and rear insert pieces 21 are formed with a respective horizontal bore therethrough which receives a respective horizontal mounting shaft that is aligned with a corresponding one of the front and rear pairs of vertically extending slots 121. The mounting shaft has opposite first and second end portions which extend respectively into the corresponding one of the slots 121 and which has a respective clamp piece 22 provided thereon.
The clamp pieces 22 are provided with externally operable locking knobs 221 respectively for forcing the clamp pieces 22 against the side walls 12 to lock the upper housing 13 at the desired position on the side walls 12.
The drawbacks of the aforementioned wood planing machine 10 are as follows:
1. The upper housing 13 can be positioned at a desired height on the machine base 11 due to the threaded engagement thereof with the threaded rods 23. When the wood planing machine 10 is in operation, the upper housing 13 is subjected to vertical forces which are applied to the threaded engagement between the threaded rods 23 and the upper housing 13, thereby resulting in the possibility of damage to the screw threads on the threaded rods 23 or in the screw holes.
2. The vertical bores in the upper housing 13 must match the pillars on the bed so as to ensure smooth sliding movement of the upper housing 13 on the pillars. However, when the wood planing machine 10 is in operation, the upper housing 13 may be subjected to uneven lateral forces which are transmitted to the pillars. As such, bending of the pillars may result to prevent future adjustment of the height of the upper housing 13.
3. Referring to FIG. 3, the conventional wood planing machine 10 further includes a rotating shaft 24 disposed between the side walls 12 and operably connected to the threaded rods 23, and a transmission shaft 26 with a transmission gear 261 mounted co-axially on the rotating shaft 24. A turning wheel unit is provided on one of the side walls 12, and includes a turning wheel 25, and a wheel axle 27 having a proximate end secured to the turning wheel 25 and a distal teethed end 271. When adjusting the height of the upper housing 13 relative to the bed, the turning wheel 25 is pressed against biasing action of a spring 28 so as to mesh the teethed end 271 of the wheel axle 27 with the transmission gear 261. This action inconveniences the user of the conventional wood planing machine.